prefer tabs over spaces for sh files

This way, we benefit from the heredoc trick based on tabs. @see
https://en.wikipedia.org/wiki/Here_document
Merge branch 'master' of github.com:greg0ire/git_template

Conflicts:
	update.sh
merge ctags and ctags-develop

flags like a, i, m or S are already supported in my non-patched version
of ctags at home, on Fedora. With a bit of detection, we can see if they are
supported or not and use the right flags at runtime.
move e option to shebang
remove 2 quotes

I think they have no use
add "required" argument
move trap after function definitions
add excludes depending on configuration option
hunt down last indention problems